When air bubbles are generated in hydraulic fluid of a hydraulic machine, and the like, the air bubbles may adversely affect a hydraulic apparatus, a hydraulic system, and the like, which use the hydraulic fluid.
Exhibit A
For example, when, in a hydraulic system used for work power transmission in construction machinery, and the like, air bubbles are mixed into the hydraulic fluid which transmits power, the air bubbles cause to reduce the stiffness of the hydraulic fluid and to promote oxidation and degradation of the hydraulic fluid, and also cause to reduce the lubricating properties of the hydraulic fluid and further to reduce the power transmission characteristics and the operating life of the apparatus.
Therefore, an apparatus or a system for effectively removing air bubbles mixed in the hydraulic fluid, and the like, has been demanded. As a conventional air bubble removing system of this kind, a system disclosed in Patent Literature 1 is known.
The air bubble removing system disclosed in Patent Literature 1 is configured by installing an air bubble removing apparatus on the side of a final return passage of a hydraulic circuit for hydraulic drive. Specifically, in a fluid system which performs suction and discharge of fluid in an oscillating tank by using a pump, the influence of the air bubbles entrained in the fluid in the tank is eliminated in such a manner that an air bubble removing apparatus, which converts the flow of the fluid into a swirling flow that causes air bubbles in the fluid to be collected on the axis center of the apparatus so as to be discharged from the apparatus, is incorporated in a return circuit to the tank, and that, after air bubbles in the fluid to be returned to the tank are removed by the air bubble removing apparatus, the fluid is introduced into the suction side of the pump.